1. Technical Field
The present invention is related to a method for constructing spanning trees, a method of redundancy, and a system; in particular to the method for constructing optimal spanning trees in real time for a hybrid network system when abnormal condition occurs within the network system, and also to the method of redundancy and the control system.
2. Description of Related Art
Software-Defined Networks (SDN) is a next generation network architecture that incorporates a centralized controller to act as a control plane of the switches of a traditional distributed network system. The architecture of the software-defined network allows the switches in the network to process the traditional data plane since the control plane is at the controller. The centralized controller provides the optimized control for the system.
The centralized architecture of software-defined network implements topology optimization and renders better routings by the controller. The communication between the controller and switches is made through standard and open protocols such as the OpenFlow protocol. The OpenFlow protocol allows the manufacturers to develop the compatible devices rather than using their own standards. The standardized architecture allows the network administrator to program or optimize applications of the controller due to the practical need. Therefore, the multi-functional application modules can be provided.
Thus, software-defined network is powerful and advantageous to the network development, and is able to dominate the future network systems. However, it is difficult to make SDN switches substitute for all the legacy network switches within a short period of time when the SDNs want to replace the legacy networks. The software-defined network may not be widespread so soon because the SDN switches are expensive and test for the substation requires great time. The centralized mechanism of management for the software-defined network may limit its network scale. Therefore, it requires a transition period for adjustment when the SDNs progressively substitute for the legacy networks. In the transition period, both the software-defined networks and the legacy networks coexist in a hybrid network.
In the hybrid network, the tangible network topology may exist loops due to fault tolerance is provided. The loops in the network may cause the notorious packet broadcast storm that will result in serious problem. Therefore, a spanning tree protocol is required to solve the packet broadcast storm problem. However, since the spanning tree protocol adapted to the software-defined network is not compatible to the spanning tree used in the legacy network, the spanning tree protocol for the legacy network does not function within the software-defined network. It is impossible to provide an overall spanning tree protocol over the topology of the hybrid network. The packet broadcast storm may still cause the problem in the loops of the hybrid network.